GU to Uniqlo clothing size

The short answer

GU S is Uniqlo XS by the two brands' own charts. 1 of 7 GU sizes land on a different label at Uniqlo.

Both brands publish the body bust each size is cut for, so every row matches a bust, not a letter or a number.

Every GU Japan sizing size read across to Uniqlo Japan sizing. Letter sizes on the left, Letter on the right.
GU Japan sizing	GU builds it for	Uniqlo Japan sizing, by chart	Same label	Uniqlo builds it for	Uniqlo also prints
XS	bust 27.6 to 29.5 in, waist 21.3 to 23.2 in, hip 30.3 to 31.9 in	XS	XS	bust 28.7 to 31.1 in, waist 22.4 to 24.8 in, hip 31.5 to 33.9 in	JP 5
S	bust 29.5 to 31.5 in, waist 23.2 to 24.8 in, hip 31.9 to 33.5 in	XS	S	bust 28.7 to 31.1 in, waist 22.4 to 24.8 in, hip 31.5 to 33.9 in	JP 5
M	bust 31.5 to 33.5 in, waist 24.8 to 26.4 in, hip 33.5 to 35 in	M	M	bust 31.9 to 34.3 in, waist 25.6 to 28 in, hip 34.7 to 37 in	JP 9
L	bust 33.5 to 35.4 in, waist 26.4 to 28 in, hip 35 to 36.6 in	L	L	bust 33.5 to 35.8 in, waist 27.2 to 29.5 in, hip 36.2 to 38.6 in	JP 11
XL	bust 35.4 to 37.8 in, waist 28 to 30.3 in, hip 36.6 to 38.6 in	XL	XL	bust 35.8 to 38.2 in, waist 29.5 to 31.9 in, hip 38.6 to 40.9 in	JP 13
XXL	bust 37.8 to 40.2 in, waist 30.3 to 32.7 in, hip 38.6 to 40.6 in	XXL	XXL	bust 38.2 to 40.6 in, waist 31.9 to 34.3 in, hip 40.9 to 43.3 in	JP 15
3XL	bust 40.2 to 43.3 in, waist 32.7 to 35.4 in, hip 40.6 to 43.3 in	3XL	3XL	bust 40.6 to 42.9 in, waist 34.3 to 36.6 in, hip 43.3 to 45.7 in	JP 17

Tinted rows change label or sit between two sizes. Read from the two charts only; no formula and no averaging.

What wearers say

Charts describe a garment, not a fit. We do not collect fit reports for this category yet, so this table is the two brands' own claims and nothing more.

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Sources

GU Japan sizing size guide, read on 2026-09-25.
Uniqlo Japan sizing size guide, read on 2026-09-25. Uniqlo on TrueToSize

Uniqlo to GU